Transcript Frostbite and Hypothermia

Cold Weather Emergencies
Victor Politi, M.D., FACP
Medical Director SVCMV-Physician Assistant Program
The Case of Tommy
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23h10
Call from MD working in James Bay
Male, 27 y.o. Unresponsive.
Found in snow, cross-country skiing
Normal Airway. Breathing.  O2 sat.
Femoral pulse + (35)  BP.
GCS=3 TR = 28C.
IV. Monitor. Mask with 100% O2
Frostbite
The Case of Tommy…
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Friend told MD:
–  PMH.  Rx.  drugs.  EtOH
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Major foot deformity
Looks like fell in ski and could not return
home by himself…
MD has some questions for you…
The Case of Tommy…
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Should he intubate? Are there risks to
precipitate dysrythmias?
• Cold myocardium prone to arythmias?
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How should he rewarm the patient?
• Danger of afterdrop?
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He wants an ABG but should he ask for
the blood to be warmed to normal T
for analysis…or it doesn’t matter?
Answer: You’ll call him back…
The Case of Tommy…
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MD calls you back 30 minutes later
Pt in cardiac arrest : V.fib. Now
27C
3 shocks
Epinephrine + re-shock
Having Amiodarone prepared…
How long should he do CPR and
rescussitation?
Answer ?
Anything wrong ?
Introduction
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EtOH 
Mental illness 
Homelessness 
Province of Quebec  Cold
Plan
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Definitions
Physiology
Pathophysiology
Labs findings : ABG, ECG
Rewarming methods
Afterdrop
ACLS 2000 guidelines
Definitions
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Primary VS Secondary
Primary
– Normal thermoregulation
– Overwhelming cold exposure
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Secondary
– Abnormal thermogenesis
– Multiple causes
Definitions
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Hypothermia : < 35C
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Mild : 32-35C
Moderate : 28-32C
Severe : < 28C
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Physiology: Heat production
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Basal metabolism (Metabolic rate)
– Heart / Liver
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Anterior hypothalamus
Thyroid / Sympathetic
Preshivering muscle tone (2x)
Shivering (2-5x)
Posterior hypothalamus
Physiology: Heat dissipation
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Radiation (55-65%)
• Gradient between environement and exposed
body area.
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Conduction (2-3%)
• Direct contact with cold substance
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Convection (10-15%)
• Wind…
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Evaporation (20-35%)
Physiology…
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Above 32C:
– Vasoconstriction
– Shivering
– Basal metabolic rate
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Below 32C:
– No shivering
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Below 24C:
– No basal metabolic rate
Pathophysiology
Cardiovascular
– Initial tachycardia
– Gradual bradycardia : HR 50% at
28C.
– Not consistent ?
• Hypoglycemia, intoxication,
hypovolemia,…?
– Refractory to atropine
–  BP  CI
– A.fib (T < 32C)
– V.fib (T < 28C)
Pathophysiology…
CNS
– Cerebral metabolism  6% / 1C
– Normal autoregulation until 25C
– EEG flat at 19C
Renal
– Cold diuresis
• Peripheral vasoconstriction
• Failure to reabsorb Na+ and water.
Pathophysiology…
Respiratory
– CO2 production  50% at 30C
– Decreased RR
– ARDS possible
Hematology
– Hemostasis and coagulation
impaired
– Problems with CPB
Mild (> 32C)
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Increase metabolic rate
Maximum shivering thermogenesis
Amnesia / dysarthria / ataxia
Loss of coordination
Tachycardic, tachypneic
Normal BP
Moderate (28– 32C)
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Stupor
No shivering
Bradycardic / A.fib
 BP  RR
Pupils dilated (< 30C)
Severe (<28C )
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Coma
No corneal or oculocephalic
reflexes
 BP
V.fib (Maximum risk: 22C)
Apnea
Asystole
Areflexia / fixed pupils
Flat EEG (19C)
Lab findings : ECG
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Woman, 75 y.o
Found unconscious in her apartment
Osborn (J) Wave
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Mr. John J. Osborn in the
early ’50’s.
When T< 33C
25%-30% of patients
Positive-negative
deflection
Osborn JJ: Experimental hypothermia: respiratory and blood pH changes
in relation to cardiac function. Am J Physiol 1953; 175:389.
Osborne (J) Wave…
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Amplitude
proportionnal to
degree of
hypothermia
Usually V3-V6
At junction of QRS
and ST segment
Osborn JJ: Experimental hypothermia: respiratory and blood pH changes
in relation to cardiac function. Am J Physiol 1953; 175:389.
ECG in Hypothermia
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Muscle tremors artifacts
Early changes
– Bradycardia
– T wave inversion
– Prolonged PR, QRS and QT intervals
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A.fib when T < 32C
V.fib when T < 28C
Lab findings : ABG
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Man, 45 y.o,.
Rectal T= 30C. LOC Intubated.
Acid-base status?
Technician asks you if he should
warm the blood before analysis…
A) Don’t warm it : 30C
B) Warm it to 37C
C) heu…(30+37)/2….33.5C
D) Both and I’ll pick the best one.
ABG in Hypothermia
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1st ABG (30C):
• pH = 7.5
• pCO2 = 27
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The Good One !!!
2nd ABG (37C):
• pH = 7.4
• pCO2 = 40
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Which one do you pick?
Will you try to  RR or VT to  pCO2 ?
Everything’s perfect, I don’t touch the
ventilator ?
The answer ? ….
ABG in Hypothermia…
…the rationale
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pH of water at any given T defines
neutrality
H2O  H+ + OHAs T , less free H+ and OH- are
generated and pH of neutrality .
As T , CO2 content is the same but
pCO2 .
Delaney KA and al. Assessment of Acid-Base Disturbances in Hypothermia
and their physiologic consequences. Ann Emerg Med, Jan 1989; 18:72-82.
So…
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1st ABG (30C):
• pH = 7.5
• pCO2 = 27
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2nd ABG (37C):
• pH = 7.4
• pCO2 = 40
ABG in Hypothermia…
…the rationale
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ABG machines usually warms
blood to 37C.
So use the UNCORRECTED ABG
for normal T .
Delaney KA and al. Assessment of Acid-Base Disturbances
in Hypothermia and their physiologic consequences. Ann
Emerg Med, Jan 1989; 18:72-82.
Rewarming methods :
Passive rewarming
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Endogenous heat production
– Shivering, metabolic rate, TSH,
sympathetic,…
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Involves decreasing heat loss
– Remove from cold environnement
– Remove wet clothes
– Provide blanket
Passive rewarming…
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O2 consumption can > 90%
CO2 production can by 65%
Possible anaerobic metabolism
Rewarming rate : 0.5C - 2.0C /h
Method of choice for mild
hypothermia
Adjunt for moderate hypothermia
Rewarming methods :
Active external rewarming
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Heat to body surfaces
– Heating blankets (fluid filled)
– Air blankets
– Radiant warmers
– Immersion in hot bath
– Water bottles / Heating pads
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Less effective than internal
rewarming if vasoconstricted +++
Active external rewarming…
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Concern about afterdrop.
Rewarming rates : 1C – 2.5C / h
Circulatory problem may be  by
applying devices to trunk only.
Very few prospective controlled
study comparing methods.
Forced Air Blankets
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ED patients
Moderate to severe hypothermia (< 32C)
Exclusion criteria
– Cardiac arrest
– Hypothalamic lesions
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16 patients
Randomized to passive insulation with cotton
blanket or forced air blanket @ 43C .
Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental
Hypothermia, Ann Emerg Med, April 1996; 27:479-484.
Forced Air Blanket…
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All patients: warm iv fluids @ 38C
Warm O2 (40C)
End point: T = 35C
Looked at:
– Rates of rewarming
– Skin damage by blankets
Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental
Hypothermia, Ann Emerg Med, April 1996; 27:479-484.
Forced Air Blanket…
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Results
No afterdrop in both groups
No skin erythema/damage
Rewarming rates (p=0.01)
– Forced-Air: 2.4C / h
– Regular blanket: 1.4C / h
Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental
Hypothermia, Ann Emerg Med, April 1996; 27:479-484.
Forced air
Mark T. Steele and al. Forced Air Speeds Rewarming in Accidental Hypothermia, Ann
Emerg Med, April 1996; 27:479-484.
Electrical heating blanket
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Carbon fiber-resistive blanket
VS Passive rewarming
8 patients
Induced-hypothermia (33C)
Skin thermal flux transducer
CO2 concentration production through mask
Compared:
– rates of rewarming
– core heat content
Greif R and al, Resistive heating is more effective than metallic-foil
insulation in an experimental model of accidental hypothermia: a
randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.
Electrical heating
Results
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Core heat content >> electrical
heating
Rates  1.5C/h > with electical
heating
No afterdrop both groups
Greif R and al, Resistive heating is more effective than metallic-foil
insulation in an experimental model of accidental hypothermia: a
randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345.
Rewarming methods :
Active internal (core) rewarming
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Warm iv fluids
Warm, humid oxygen
Peritoneal lavage
Gastric / Esophageal lavage
Bladder / Rectal lavage
Pleural / Mediastinal lavage
Microwaves (Diathermy)
Extracorporeal circulatory
rewarming
Warm iv fluids
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Up to 45C shown to be safe
65C fluid studied in dogs
– Journal of Trauma 1993 (8 dogs)
– American Journal of Surgery 1996 (10
dogs)
– Through IVC
– Safe. No Complications
– 2.9C/h compared to 1.25C/h (J
Trauma)
– 3.7C/h compared to 1.75C/h (Am J
Surg)
Warm iv fluids…
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Saline…Not RL
Long tubulure = lost of heat
Can use microwave for saline (No
D5W)
– Annals of EM, 1984 and 1985
– 1L of NS to 39C : 2 minutes at high power.
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No microwave rewarming for PRBC
– Hemolysis
– Hemoglobinuria
– Transfusion reaction
Warm, humidified O2
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42C-46C
Prevent heat loss
Negligible heat gain
Very important in management of
hypothermic patient:
– Up to 30% of heat production lost through
airway.
Gastric/Oesophageal/
Bladder/Rectal lavage
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Not shown to be better than external
rewarming.
Limited surface area
Limited heat exchange
Limited utility (!)
Recommend as last resort when other
modalities not available.
Peritoneal lavage
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Fluid at 40-45C
Up to 12 L/h
KCl free
Hepatic rewarming
Renal support when dialysate is used
2C-4C / h
C.I.
– Abdominal trauma
– Acute abdomen
– Free intra-abdominal air
Pleural lavage
Closed-thoracic lavage
Continuous thoracic cavity lavage
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Two large (38F) ipsilateral chest tubes
1: 2nd or 3rd anterior intercostal space,
midclavicular.
2: 5th or 6th intercostal space, posterior
axillary line.
NS or tap water @ 42C
Rewarms heart + greater vessels
Hall KN and al. Closed thoracic cavity lavage in the treatment of severe
hypothermia in human beings. Ann Emerg Med, Feb 1990;19:204-206.
Mediastinal lavage
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Requires certain expertise
Limited clinical experience
Case reports
Internal cardiac massage
8C / h
Douglas D. Brunette, Hypothermic cardiac arrest: An 11 year review of
ED management and outcome. Am J Emerg Med 2000; 18:418-422.
Extracorporeal blood
rewarming techniques
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Hemodialysis
Arteriovenous rewarming
Venovenous rewarming
Cardiopulmonary bypass
Extracorporeal blood
rewarming…
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Hemodialysis : renal dysfunction
AV depends on the pt’s BP
CPB is the « Gold Standard ».
CPB improves long term survival and
neurologic outcome.
- 15 of 32 long term survivors and none had
neurologic deficits (7 years later).
B.H. Walpoth and al. Outcome of survivors of accidental deep hypothermia and
circulatory arrest treated with extracorporeal blood warming, N Engl J Med,
1997;337:1500-5
Diathermy
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Ultrasonic waves
Microwaves
Short waves
Few studies
Radio wave regional
hyperthermia: Experience with Tx
of tumors.
Not widespread because of
dosages in human poorly defined.
Diathermy…
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Prospective
Radio Wave vs.
Peritoneal lavage
6 dogs
Rate of
rewarming 3x >
for Radio wave.
J.D. White and al. Controlled comparison of Radio Wave regional hyperthermia and
peritoneal lavage rewarming after immersion hypthermia, J Trauma, 1985; (25)10:
989-993.
The Afterdrop Phenomenon
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Continued fall in deep core T during the initial
period of rewarming.
First described by James Currie in 1798
Theory of Burton and Edholm (1955):
– Attributed to peripheral vasodilatation
– Return of cold blood to central circulation
– Cooling of myocardium
Accepted theory until mid ’80’s
Burton, A.C., and O.G. Edholm. Man in Cold Environment. London: Arnold, 1955, p.216.
Paul Webb,
An alternative explanation.
J. Appl. Physiol. 1986
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Fall of T during active rewarming:
– Up to 2C
– 10 – 30 min
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Used calorimeter, rectal,
esophageal and tympanic probes.
Heat loss calculation
Webb, Paul. Afterdrop of body temperature during rewarming: an alternative
explanation. J.Appl.Physiol. 60(2): 385-390, 1986.
2 mecanisms for afterdrop
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Convection mecanism
– Return of cold blood from periphery
– Minimal is any contribution
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Conduction mecanism
– Thermal gradient principal
– Heat flow principal
Webb, Paul. Afterdrop of body temperature during rewarming: an alternative
explanation. J.Appl.Physiol. 60(2): 385-390, 1986.
Conduction Mecanism
Environement
Skin/Tissues
Blood vessel
Heat transfer
Heat transfer
Afterdrop: an alternative
explanation
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Active external rewarming  increase
threat of further cooling of the heart…as
much as thought before.
Correlated by many other papers
•Savard, G.K., K.E. Cooper, W.L. Veale, and T.J. Malkinson. Peripheral blood flow
during rewarming from mild hypothermia in humans. J. Appl. Physiol. 58(1): 4-13,
1985.
•Romet, Tiit T. Mechanism of afterdrop after cold water immersion. J.Appl.Physiol.
65(4): 1535-1538, 1988.
Freezing Injury Cascade
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Prefreeze phase
Freeze-thaw phase
Vascular stasis and progressive
ischemia
In The ED - Prethaw
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After stabilizing core temperature and
addressing associated conditions prepare to initiate rapid thawing
Protect part
Stabilize core temperature
Hydration
No friction massage
In the ED - Thaw
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Rapid rewarming in 38-410 C circulating
water until distal flush (thermometer
monitoring)
Requires 10-30 min with active motion
of part without friction massage
Parenteral analgesia
In the ED - Postthaw
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Clear vesicles -aspirate (if intact) vs.
debride
Hemorrhagic vesicles - aspirate
Apply topical aloe vera (Dermaide)q6h
Ibuprofen 400mg q 12h
Tetanus prophylaxis
Streptococcal prophylaxis for 48-72hr
Elevation
Management: ED issues
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Intubation
General belief it can induce arythmias
Danzl, Multicenter Hypothermia Survey,
Annals Emerg Med, Sept.87.
– Data from 13 ED
– 428 cases
– 117 intubation
– NO arythmias
Management: ED issues
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Bretylium
Recommended for V.fib in hypothermia
Removed from new ACLS 2000:
•  availability and limited supply
•  occurrence of side effects
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Still recommend in textbooks (Rosen)
Recommended by US Wilderness
Emergency Medical Services Institute
Based on Dogs studies
Good for prophylaxis only
Management: ED issues
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Drugs / Shocks
NO drugs if T < 30C
– Not efficacious
– Not metabolised
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If > 30C,  intervals between
doses
If < 30C and failure of 3 shocks
Defer subsequent shock
+ Rx until T > 30C
Sequelae
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Neuropathic
pain
– phantom
– causalgia
– “Tabes” burning
– chronic
Sequelae
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Thermal sensitivity
– heat
– cold
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Sensation
– hypesthesia
– dysesthesia
– paresthesia
– anesthesia
Sequelae
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Autonomic dysfunction
– Hyperhidrosis
– Raynaud’s
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Musculoskeletal
– atrophy,compartment syndrome
– rhabdomyolysis, tenosynovitis, stricture
– epiphyseal fusion, osteoarthritis
– osteolytic lesions,necrosis,amputation
Sequelae
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Dermatologic
– edema
– lymphedema
– chronic/recurrent ulcers
– epidermoid/squamous carcinoma
– hair/nail deformities
Sequelae
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Miscellaneous
– core temperature afterdrop
– acute tubular necrosis
– electrolyte fluxes
– psychic stress
– gangrene
– sepsis
Conclusion
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Hypothermia is rare but treatable
Good outcome after prolonged
arrests
Include Hypothermia in your  Dx
Include T as a 5th vital sign…
Call early to organize CPB if
available if patient in cardiac arrest
Prevention is still the best
Other Causes of Hypothermia
The Alcatraz/San Francisco
Swim Study
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San Francisco Bay…contest…
Swims from Alcatraz Island to shore
No wetsuits or protective clothing
Water T = 12C (53F)
Outside : T = 10C
3 Km
11 subjects for study
23 y.o to 70 y.o (!)
Measured T after contest.
Thomas J. Nuckton and al. Hypothermia and afterdrop following open water
swimming: The Alcatrax/San Francisco Swim Study. Am J Emerg Med 2000;
18:703-707.
Afterdrop conclusion
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Rectal T lags behing esophageal T
and is often > than esophageal and
pulmonary T.
Think about it but you can probably not
prevent it.
Issue with active external rewarming
Other concerns about external
rewarming:
– Acidosis
– Hypotension
Questions ???